In hard disk drives (magnetic recording), it is generally desired to increase the density at which information is recorded on the disks as this leads to higher storage capacity and/or reduced cost. Currently the disk drive industry is facing a significant challenge in increasing storage density due to a problem of thermal stability: The very small volumes of magnetic material containing each bit of recorded information become unstable due to thermal agitation. A possible solution is to use a different material in the magnetic recording layer on the disk that has a larger anisotropy or coercive field. However, presently available materials used in magnetic recording heads cannot produce sufficient magnetic field to write on such high-anisotropy media. The problem is thus that the coercivity of the recording medium needs to be simultaneously low for writeability and high for thermal stability. Several approaches to get around this problem are being explored by the industry, including heat assisted magnetic recording (HAMR)(also called thermal-assisted magnetic recording) in which the recording layer is heated temporarily and locally by a focused laser beam or using microwaves.
In HAMR, reliable operation of the near field optical transducer used to focus the laser remains problematic. Additionally, the resulting high temperatures on a disk can degrade the lubricant on its surface.